Coaxial cable connection means



Nov. 3, 1970 c. w. LANHAM, JR

COAXIAL CABLE CONNECTION MEANS 2- Sheets-Sheet 1 Filed Sept. 17, 1968INVENTOR Char/es W La n/2am, Jr

urrrlilll i 4 A s -m@ ATTORNEY C. W. LANHAM, JR

COAXIAL CABLE CONNECTION MEANS Nov. 3, 1970 2 Sheets-Sheet 2 Filed Sept.17, 1968 INVENTOR Char/es W. Lon/mm, Jr.

. f wzzmvu 8 9 AN ATTORNEY United States Patent 3,538,487 COAXIAL CABLECONNECTION MEANS Charles W. Lanharn, Jr., Silver Spring, Md., assignorto Entron, Inc., Silver Spring, Md., a corporation of Delaware FiledSept. 17, 1968, Ser. No. 760,252 Int. Cl. H01r 13/58, 17/18 U.S. Cl.339-95 13 Claims ABSTRACT OF THE DISCLOSURE Connector means adapted forconnection with at least one coaxial cable having an inner conductorthat extends a given distance beyond a spacer insulation layer and anouter conductor, characterized by the provision of a conductive tubularbody having at one end a bore for receiving a cable end, non-conductiveadhesive means curable to permanently bond said cable end to said body,retaining means for preventing withdrawal of the cable end from the bodyduring the curing of the adhesive, and means electrically connectingsaid body with said outer conductor. In one embodiment the connectormeans comprises a splice for electrically connecting the ends of a pairof cables, and according to another embodiment, the connector meanscomprises a terminator for connecting a load impedance between the freeends of the conductors.

This invention relates to an improved connector construction for coaxialcables.

In the patented prior art, various types of devices have been proposedfor splicing together in electrical and mechanical engagement a pair ofelectrical coaxial cables. For example, in the conventional flare typeof connection, the spacer insulation between the concentrically arrangedconductors is reamed out, ferrule means are arranged to extend at eachend in the reamed out portions of the cables, and an outer body memberis threadably connected with the ferrule means to axially tighten theassemblage and to eifect both mechanical support and electricalconnection of the cable. While the flare type of connection affordsrelatively high mechanical strength, the components are ratherexpensive, and the assembly of the parts is time consuming and requiresspecial tools.

The use of grip ring means for retaining the components of an electricalconnector against axial withdrawal is also known in the art, asevidenced by the Canadian Pat. No. 711,356, and the U.S. patents toMatthysse No. 3,019,283, Ustin No. 2,870,239 and Fuller et al. No.3,288,914. Furthermore, the use of electrically conductive adhesivemeans has been proposed for both mechanically and structurallyconnecting together a pair of conductive electrical components.

The present invention was developed to provide improved coaxial cableconnector means that provide extremely great structural strength, thatare water and pressure tight, and that allow for the expansion andcontraction of the coaxial cable.

The primary object of the present invention is to provide improvedconnector means for coaxial cables wherein great structural strength isobtained through the use of an extremely strong non-conductive adhesivefor bonding together the structural parts.

A more specific object of the invention is to provide connector meansincluding a conductive body containing a bore for receiving one end of acoaxial cable, non-conductive adhesive means curable to permanently bondthe cable to the body, retaining means preventing withdrawal of thecable from the body during the curing of the adhesive, and meanselectrically connecting said body with the outer conductor of the cable.Preferably the non- 3,538,487 Patented Nov. 3, 1970 ICC conductiveadhesive is of the type affording a fluidand pressure-tight seal andhaving a highshearing stress (for example, an anaerobic adhesive similarto the product Loctite Tube Sealant, manufactured by Loctite Corporation of Newington, Conn). In accordance with a first ernbodiment of theinvention, the connector means comprises a splice for connecting theends of a pair of coaxial cables arranged colinearly end-to-end. Inaccordance with a second embodiment, the connector means comprises aterminator for connecting a dummy load impedance between the ends of theinner and outer conductors at one end of a coaxial cable.

A further object of the invention is to provide connector meansincluding a retaining ring mounted in the conductive tubular body forengaging the outer conductor to prevent withdrawal of the cable from thebody. In addition or in the alternative, the retaining means may bemounted in the body for electrical and mechanical engagement with theinner conductor of the cable.

A further object of the invention is to provide connector means that arequickly assembled without the provision of any special tools. To thisend, the body member is provided with means defining at least oneinternal stop shoulder against which the cable outer conductor abuts inelectrically conductive engagement. To increase the conductivity at thisjuncture, conductive means such as wire mesh or copper spring fingersare arranged between the conductor end on the cable and the internalshoulder on the body.

Other objects and advantages of the invention will become apparent froma study of the following specification, when viewed in the light of theaccompanying drawings, in which:

FIG. 1 is a partly sectioned view of the coaxial cable splice embodimentof the invention;

FIG. 2. is a sectional view taken along line 2 2 of FIG. 1; and

FIG. 3 is a detailed sectional view of a terminator embodiment of theinvention.

Referring first to FIGS. 1 and 2, the cable splice means 2 is adapted tomechanically and electrically connect a pair of coaxial cables 4 and 6having inner conductors 8 and 10 and outer tubular conductors 12 and 14separated by annular insulation layers 16 and 18, respectively. As shownin the drawing, the end portions of the outer conductors and theinsulation of the colinearly arranged cables are removed so that theremaining bare ends of the central conductors protrude axially beyondthe insulation and the outer conductor a given distance x. As isconventional in the art, the inner conductors are formed of copper, andthe outer conductors are unitary imperforate sheaths formed from arelatively soft conductive metal, such as aluminum.

For mechanically connecting the cable ends and for electricallyconnecting the outer conductors 12 and 14, the cable splice meansincludes a tubular conductive body 20 counterbored at each end to definea stop shoulder 22, the diameter of the counter-bore being generallyequal to the outer diameter of the outer conductors of the cable. Thusthe counter bore is adapted to receive the cable end as shown, theextremity of the outer conductor terminating immediately adjacent theshoulder 22. Preferably, in order to improve the electrical connectionbetween the outer conductor and the tubular body 20, there is compressedbetween the shoulder 22 and the adjacent extremity of the outerconductor an annular layer 24 of electrically conductive woven wiremesh. In the alternative, conductive spring finger means may besubstituted for the conductive mesh. At each end, the tubular body 2 isprovided with retaining ring means 26 that engage the outer conductors12 and 14 to resist withdrawal of the cables from the tubular body 2.More particularly, each retaining ring means comprises a grip ring 28mounted in a recess contained in an enlarged flange portion 20b of thetubular body 20, said retaining ring having an effective inner diameterthat is less than the outer diameter of the outer cable conductors, theinner circumference of said ring comprising a plurality of resilient,radially inwardly directed fingers having such configurations (as isknown in the art) to engage the soft outer conductors to preventwithdrawal of the cables from the tubular body. Suitably designedwashers 32 serve to retain the rings 28 in the flange recesses. As willbe described below, preferably the enlarged flange portions 20b compriseseparate portions secured to the central part of the tubular body by anadhesive having an exceptionally high shear strength, for example, ananaerobic adhesive (such as the aforementioned Loctite product).

The inner conductors of the cable are mechanically and electricallyconnected by a conductive tubular sleeve 36 that is tightly fittedconcentrically upon the inner conductors 8 and 10. On each end of thesleeve 36 is mounted an annular spacer member 38 formed of insulatingmaterial and including a tubular hub portion 38b in engagement with thesleeve, and an outwardly divergent conical portion 38a in engagementwith the inner surface of the tubular member.

In accordance with the present invention, the counterbore wall of thetubular member 20 is permanently bonded to the outer surface of theouter conductor of the cable by a non-conductive adhesive having anextremely high shear strength (on the order of 2000 p.s.i., forexample). Similarly, the sleeve 36 is permanently bonded to the innerconductors by a similar high shear strength adhesive. Finally, theflange portion 20b carrying the retaining ring means 26 is permanentlybonded (generally at the factory) by the adhesive to the tubular body20. Preferably the adhesive is an anaerobic adhesive having a shearstrength on the order of 2000 to 5000 p.s.i. (similar, for example, tothe tube sealant grade of the product Loctite sold by LoctiteCorporation of Newington, Conn.).

In order to provide electrical connection between each outer conductorand the tubular sleeve, conductive means are provided that penetrate thenon-conductive adhesive. As shown in FIG. 2, these conductive meanscomprise pointed longitudinal ribs 19 that are carried by and extendradially inwardly from the bore wall. In the alternative, other adhesivepenetration means-such as knurled surfaces, dimples, projections or thelikemay be provided for electrically connecting the connector body withthe outer conductor.

OPERATION To effect the strong watertight electrically conductive cablesplice illustrated in the drawing, the outer conductor and insulationlayers are first stripped from the ends of the coaxial cable to exposegiven lengths x of the bare inner conductors, whereupon the ends of theinner and outer conductors are roughened and cleaned by suitableabrasive means. These roughened surfaces are then coated with theadhesive in the liquid state, whereupon the sleeve 36- is fitted uponthe bore inner conductor of one cable, and the end of that cable isinserted within one end of the tubular member 20 until the extremity ofthe outer conductor engages stop 22 to compress the wire wesh layer 24.Similarly, the other cable is inserted into the other end of the tubularmember 20 with the inner conductor being received within the conductivesleeve 36, and the outer conductor being received in the correspondingcounterbore.

Electrical connection between the outer conductors and the tubular bodyis effected by the ribs 19, and connection between the sleeve 36 and theinner conductors is effected by roughened surfaces or projections on thesleeve. Owing to the retaining action of the grip ring means, togetherwith the support of the sleeve 36 by the spacer means 38, the adhesivelyjoined surfaces are immobilized during the curing of the adhesive (whichnormally requires a period of from a matter of minutes up to severalhours, depending on conditions of ambient temperature, and humidity).Thus the grip ring means affords a temporary support strength of aboutpounds until the adhesive is completely cured, whereby the technicianmay assemble the connector and leave it during the final curing of theanaerobic adhesive.

The cable splice of the subject invention is water-tight and pressuretight and retains the inner and outer conductors against the expansionand contraction of the coaxial cable. The splice means requires only aminimum number of relatively inexpensive parts, and permits rapidconnection of the cable ends with a minimum number of tools.

It is apparent that various modifications and improvements may be madein the disclosed invention. As indicated above, to improve theelectrical conductivity between certain of the bonded surfaces (forexample, the contiguous surfaces between the outer conductor and thecounterbore walls of the tubular body, and the contiguous surfaces ofthe inner conductors and the sleeve 36), the surfaces of one part may begrooved or scored to define sharp edges that penetrate the adhesivelayer for electrical connection with the companion surfaces of the otherpart.

Referring now to the terminator embodiment of FIG. 3 the coaxial cable200 includes an inner conductor 202 that extends axially beyond theouter conductor 204 and the spacer insulation 206, said cable beingreceived in a corresponding bore contained in one end in the conductivetubular body 208. The extent of axial insertion of the cable into thebody is limited by the annular stop shoulder 210 that is in electricalengagement with the outer conductor 204. At its free extremity the borecontains a tapered surface 212 that guides the outer conductor 204somewhat during insertion of the cable in the tubular body. As in theprevious embodiment, a layer of curable anaerobic adhesive is providedon the outer surface of the outer conductor to permanently bond thecable to the body. In order to effect the forementioned electricalconnection, the wall of the tubular body 208 is provided with dimples214 that extend inwardly to penetrate the adhesive layer and therebyelectrically engage the outer conductor.

The free extremity of the inner conductor 202 is received in aconductive sleeve 216 that is rigidly supported in the tubular body bythe insulated support housing 218. To facilitate insertion of the centerconductor in the sleeve, the bore of the housing 218 includes a taperedorifice 220. The sleeve 216 is secured in the plastic housing 218 by alayer of a suitable adhesive (such as an anaerobic adhesive) and isprovided with partially punched out retaining points 222 that impale thecenter conductor to prevent withdrawal of the cable from the tubularbody 208. In the event that a curable layer of anaerobic adhesive isarranged between the inner conductor 202 and the sleeve 216, theadhesive is penetrated by the points 222 to provide the aforementionedelectrical connection.

The other end of the tubular body 208 is closed by the conductive endcap 226 that is in electrical contact with, and is fitted onto, the body208. The end cap maintains the plastic housing in engagement with theannular stop shoulder 210.

Suitable dummy load impedance components (such as a capacitor 228 and aresistor 230) are soldered between the cap 226 and the sleeve 216,thereby defining a terminal load between the inner and outer conductors.

In operation, in order to terminate a given coaxial conductor with thedummy impedance load, the outer conductor and the projecting length ofinner conductor are roughened and are coated with the anaerobic adhesivein the uncured state, whereupon the cable end is inserted in the tubularbody. Owing to the impalement of the inner conductor by the points 222,and the gripping action on the outer conductor by the bore Wall of thetubular body and the dimples 214, the cable end is retained againstwithdrawal from the tubular body during the final curing of theadhesive.

Other changes and modifications may be made in the apparatus describedwithout deviating from the invention set forth in the following claims.

What is claimed is: 1. Quick-fastening connector means adapted forconnection with one end of a coaxial cable having an inner conductorthat extends a given distance beyond successive concentrically arrangedinsulation and outer conductor layers, respectively, comprising atubular conductive body having at one end a bore for receiving saidcable end, the diameter of said bore being generally equal to the outerdiameter of said outer conductor, said body including also within saidbore integral stop means adapted to cooperate with the end extremity ofsaid outer conductor to limit the extent of axial insertion of saidcable end in said bore; a layer of curable adhesive operable, whencured, to permanently bond said outer conductor to said body;

means including said stop means for electrically connecting said outerconductor with said body when said cable end is in the fully insertedposition defined by said stop means; and

retaining means preventing withdrawal of said cable from said fullyinserted position relative to said body during the curing of saidadhesive.

2. Apparatus as defined in claim 1, wherein said adhesive layer isnon-conductive and is arranged generally concentrically between the wallof said bore and the outer surface of said outer conductor;

and further wherein said electrical connecting means comprises firstconductive means extending radially between said outer conductor andsaid bore wall to penetrate said adhesive layer, and second conductivemeans arranged between said integral means and the extremity of saidouter conductor.

3. Apparatus as defined in claim 1, wherein said adhesive means has ashear strength of at least 2000 pounds per square inch. I

4. Apparatus as defined in claim 3, wherein said adhesive meanscomprises an anaerobic adhesive.

5. Apparatus as defined in claim 1, wherein said retaining meanscomprises a retaining ring mounted in said bore, said retaining ringhaving a plurality of radially inwardly directed spring fingers adaptedto engage said outer conductor to prevent withdrawal of said cable fromsaid body.

6. Apparatus as defined in claim 1, wherein said retaining meanscomprises means mounted in said tubular body for engagement with saidinner conductor to prevent withdrawal of said cable from said body.

7. Apparatus as defined in claim 6, wherein said retaining meanscomprises a conductive sleeve;

and insulating means supporting said sleeve in said tubular body toreceive said inner conductor when said cable end is inserted in saidbore, said sleeve including projection means adapted to impale saidinner conductor to prevent withdrawal of said cable end from said body.

8. Apparatus as defined in claim 7, wherein said connector meansincludes an impedance load electrically connected between said sleeveand said tubular body, whereby said connector means serves as a cableterminator.

9. Apparatus as defined in claim 1, wherein said tubular body containsin its other end another bore for receiving a second coaxial cable endthe inner connector of which extends axially beyond the outer conductorand the space insulation layer; and further including stop meanslimiting the extent of axial insertion of said cable ends in saidtubular body;

an additional layer of curable non-conductive adhesive operable, whencured, to permanently bond said outer conductor to said body;

further retaining means for preventing withdrawal of said second cableend from said body during the curing of said adhesive; and

means electrically connecting said tubular body with the outer conductorof said second cable, whereby said connector means comprises a splicefor electrically connecting the outer conductors of said cables.

10. Apparatus as defined in claim 9, and further including a conductivesleeve mounted coaxially upon and electrically connecting the innerconductors of said cables.

11. Apparatus as defined in claim 10, and further including a thirdadhesive layer curable to permanently bond said sleeve to said innerconductors.

12. Connector means as defined in claim 11, and further includingannular spacer means supporting said sleeve within said tubular body,said spacer means comprising at least one annular spacer member formedof insulating material and arranged concentrically upon said sleeve.

13. Connector means as defined in claim 12, and further wherein saidspacer means includes a pair of said spacer members arranged at oppositeends of said sleeve, respectively, each of said spacer members includinga hub portion fitted upon the end portion of said sleeve, and anoutwardly diverging conical portion the extremity of which engages theinner wall surface of said body.

References Cited UNITED STATES PATENTS MARVIN A. CHAMPION, PrimaryExaminer L. J. STAAB, Assistant Examiner US. Cl. X.R

